docs: def unset(self, key):
          """
          Remove a key from the database entirely.
          """
          self.cursor.execute('delete from kv where key=?', [key])
          if self.revision and self.cursor.rowcount:
              self.cursor.execute(
                  'insert into kv_revisions values (?, ?, ?)',
                  [key, self.revision, json.dumps('DELETED')])